MRG, FIX: Fix single time point

[larsoner]

Alternative to #7518.

I think we should show the (incorrectly-named) _TimeViewer even if there is a single time point because it shows useful controls like clim, view, etc. (and others if we add them later). This hides the playback speed and time slider as well.

[codecov]

Codecov Report

Merging #7520 into master will decrease coverage by 0.00%.
The diff coverage is 65.62%.

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##           master    #7520      +/-   ##
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- Coverage   90.13%   90.12%   -0.01%     
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  Files         452      452              
  Lines       82947    82987      +40     
  Branches    13113    13117       +4     
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+ Hits        74762    74792      +30     
- Misses       5350     5361      +11     
+ Partials     2835     2834       -1     

[larsoner]

Pushed a commit to fix the PyQt-abort-on-error problem

[GuillaumeFavelier]

How do we select the functions wrapped by safe_event? Because I would like to suggest self.play() as well.

[larsoner]

In principle, anything that could cause an error should be guarded. But in the special case of play we probably want to do more, because we should stop the playback, otherwise the user will get spammed with messages

[larsoner]

@GuillaumeFavelier @agramfort this should be ready for review/merge now

[agramfort]

@GuillaumeFavelier please merge if you're happy. You know this code better than me

[GuillaumeFavelier]

LGTM @larsoner, I tested it and it works even when only one time step is available. We should think about a better name for this wrapper 😄

I think a bit more work is needed in order to display the final (updated) state of _TimeViewer when it's ready only at the end. For instance, the sliders are displayed as soon as they are added. We don't have the option to add them to the scene while hidden and just toggle the interface for example. We can take care of that in another PR, I think it was reported somewhere.

[larsoner]

Maybe it would require a PyVista PR? Or is there some general VTK renderer update blocking that we could use?

[GuillaumeFavelier]

I think a trick similar to https://github.com/mne-tools/mne-python/blob/master/mne/viz/_brain/_brain.py#L947-L963 would be necessary where we configure the representation of the widget to be hidden by default. This would require a PR on pyvista.

is there some general VTK renderer update blocking

hm... I don't know any. I tried hiding the window (or interactor) and display at the end but although the window reappears ready, there is the fact that it disappears out of the blue.

[GuillaumeFavelier]

Maybe the rendering thread could be paused...
EDIT: it won't work because update() is called at multiple places

Reference: https://github.com/pyvista/pyvista/blob/master/pyvista/plotting/qt_plotting.py#L449